We put so much faith into the automated and computerised systems used to book flights that it’s hard to believe that sometimes things can go wrong.

First, US Airways passengers who had their boarding passes sent to their mobile phones, found that a glitch in the system had produced passes with the wrong names or flight numbers. The airline said it affected passengers using the US Airways mobile site or app, which had been rolled out this summer. The problem was finally fixed after about three hours.

The next, much more fortuitous blunder came from United, when for a couple of hours the computer system accidentally loaded $0 fares and sold them on its website.

Word spread on Twitter and even with airport charges, some passengers got tickets for just $5 or $10. Once the airline found out what was happening it shut the website down “for a couple of hours.” The site was back up by 2.30pm New York time, and so were the prices. United has not yet decided if it will honour the tickets.